Twitter on Thursday debuted a dramatically different new user interface for all versions of the micro-blogging service: The company will be rolling out totally new versions of the desktop website, mobile website, native mobile apps, and Tweetdeck to its more than 100 million users over the next few weeks.

The new design gives Twitter users the ability to navigate the service through four basic methods: “Home,” “connect,” “discover,” and “activities.”

Complex capabilities, simpler navigation

Though during the launch event at Twitter’s San Francisco headquarters, CEO Dick Costolo and founder Jack Dorsey repeatedly said that the redesign was aimed at making the Twitter experience “simpler,” the new version of the site is in many ways richer and more complex than ever.

That’s not meant to sound like a negative thing: The new UI makes it much easier to find and access context and content around each Tweet, as well as find new Twitter accounts to follow that are relevant to you. The search capabilities are now navigable even for people who don’t know what a “hashtag” is. In essence, the new version of Twitter is stickier than ever, and accessible to a wider group of people — both qualities that the company has long been looking to enhance.

The Discover tab on Twitter (click to enlarge)

Twitter as news source

The redesign also positions Twitter as an accessible source for news in a way that it hasn’t done before. The site’s new “discover” tab may be the most important element of the redesign as it presents the most relevant, newsy content on Twitter in a way that’s personalized to each user.

This could solve the problem that many people see with Twitter: They don’t use the site because they “don’t have anything to say.” Now, Twitter is positioning itself as a valuable service for everyone, whether they actively contribute content to the site or not.

“I think we’ll see a growing number of users who come to Twitter every day and don’t Tweet,” CEO Dick Costolo said to a group of reporters after the official launch event finished.

Better for brands — and revenue

Brands can have a elevated place in the new Twitter design, which makes sense given the company’s necessary push for revenue: At six years old, Twitter now has 700 employees and has taken on more than $1 billion in venture capital. The redesign gives brands, celebrities and businesses “enhanced” profile pages. At launch, only a select group has access to these pages — American Express and The Red Cross are among them — but eventually they will be available to any business. Enhanced brand pages are free, but ostensibly they will make companies see how many of their customers are using Twitter and could entice them to buy ads on the site.

In all, it’s a very smart move for Twitter. For months, I’ve heard people grumble with frustration about Twitter’s user experience basically staying the same for so long. “They have scores of great engineers, heaps of money, millions of users. What in the world are they doing over there?” Now we have the answer, and in general it’s looking pretty good.